Devices for wireless power transmissions via rotatable bodies are conventionally known (for example, refer to Patent Literature 1). In a conventional structure disclosed by this Patent Literature 1, a transmission/reception unit (a transmitting antenna and a receiving antenna) is disposed with the central axis of a rotatable body (a shaft) being approximately centered in the transmission/reception unit, or is disposed around the central axis, and electric power is transmitted from the transmitting antenna to the receiving antenna by magnetic field coupling. Further, by disposing plural transmission/reception units, multiple power transmissions can be carried out.